An array camera is a type of a light-field camera. The array camera comprises an array of micro camera lenses enabling to capture 4D light field information about a scene. Such light field information can be used to improve the image of a scene by use of an image editing software in a computer.
This technology is now about to enter the consumer camera market. The potential of lowering the height of the camera compared with traditional technology is one of the advantages appreciated by the manufacturing industry of wireless devices, such as mobile terminals or mobile phones. Some other known features are high dynamic range imaging, post processing focusing and control of depth of field.
Traditional Complementary metal-oxide-semiconductor (CMOS) cameras have what is known as a rolling shutter. The individual pixels are not integrating the signal produced by light to electricity conversion simultaneously but rather in a “rolling” fashion starting at one corner of the sensor and progressing across rows horizontally iterating vertically line by line until the last pixel located in the opposite corner of the starting pixel is reached. Typically this iteration is performed in a first step as resetting the pixels and thereby starting the integration. In a second step the signal is read as the pixels are iterated whish thereby is the end of the integration.
The rolling shutter causes an effect known as motion distortion. The integration time, or exposure time, might be short enough to freeze the motion of a moving object providing a sharp image. But the object is depicted distorted as the object moves from the moment the first pixel is exposed until the last pixel is exposed.
Yet another problem with the rolling shutter is observed when a flash is used. All the pixels have to integrate light simultaneously during the short duration of the flash light. This requirement makes the usage of a short duration flash, e.g. a Xenon flash, difficult.
A so called global shutter allows all pixels to integrate light simultaneously which solves both of the above mentioned problems. Global shutter designs that are integrated in the semiconductor image sensor have been developed. There are however disadvantages and also problems to overcome with this design. A known problem is to integrate an electrical global shutter into a wireless device such as a mobile phone.
A mechanical global shutter has been used in some cameras to solve the problems in a satisfying way. The integration of light is typically started with the shutter open by resetting all pixels simultaneously. The integration is stopped by closing the shutter and thereby covering the lens opening. The sensor is then read in a rolling mode which is feasible as they are protected from light exposure.
A typical mechanical shutter design is placed on top of a mobile phone camera. The array camera is however typically much lower in height than a traditional camera. The height may be as low as 60% in a comparison. This leaves room for a mechanical shutter in the case of an array camera while still maintaining a reasonable low height.